Conventionally, in assembling constitutional components at the time of manufacturing a loud speaker, an operation has generally been difficult to perform mechanically, and has been dependent upon a skilled manual operation.
However, recent loud speakers with reduced size and thickness have been increasingly affected by displacement of components due to the manual operation, thereby decreasing a yield.
Especially when a magnet as one of the constituent components of the loud speaker is reduced in size in accordance with the reduced size and thickness of a loud speaker body, the yield decrease is obvious
Specifically, when the magnet is reduced in size, a gap between a plate and a yoke is required to be narrowed for compensating deterioration in performance due to the size reduction, but it has been difficult in the manual operation to accurately dispose respective magnetic circuit components of the plate, the yoke and the magnet which constitute a magnetic circuit body of the loud speaker, and a voice coil may come into contact with the plate and the yoke, leading to the yield decrease.
To approach this problem, there is described in Patent Document 1 a loud speaker manufacturing method where each magnetic circuit component is accurately disposed by use of a jig to allow the gap narrowing.
FIGS. 18A to 18D are views showing a conventional loud speaker manufacturing method. In the manufacturing method described in Patent Document 1, as shown in FIGS. 18A to 18D, plate 103, magnet 104 and yoke 105 are sequentially piled up using first jig 101 and second jig 102, to manufacture a magnetic circuit body of the loud speaker. This can result in such accurate disposition that magnet 104 is placed at a center of yoke 105, and further, a center axis of magnet 104 and a center axis of plate 103 are placed on the same axis.
The conventional manufacturing method described in Patent Document 1 has a problem of decreased production efficiency caused by the use of two different jigs of first jig 101 and second jig 102.
Further, in the case of the voice coil being unable to accurately perform vertical vibration inside the narrowed magnetic gap, the voice coil comes into contact with the plate and the yoke at the time of driving the loud speaker, and the yield may thereby decrease.